Fog nets are a literal lifesaver in arid regions with regular fog – but unfortunately they can also capture airborne pollution. Scientists at ETH Zurich have now developed fog nets that can use sunlight to break down hazardous molecules.
Rain is rare in many regions, but for some, such as the mountains of northern Chile, water-dense fogs roll in regularly in a frustrating show of irony. The droplets in these fogs are usually too small to fall as rain, but can condense on certain surfaces. Locals have long taken advantage of this and used fog nets to collect water in useful quantities and funnel it into pipes and tanks.
In many places though, atmospheric pollution can contaminate that collected water, making it potentially unsafe to drink or even cook with. So for the new study, researchers at ETH Zurich developed a new type of fog net that purifies the water it captures.
The net is made up of metal wire coated with certain polymers as well as titanium dioxide. The polymer mix is designed to maximize the efficiency of droplet formation, and ensure they run down the mesh as quickly as possible. Meanwhile, the titanium oxide works as a chemical catalyst, breaking down organic compounds when exposed to UV in sunlight.
The team tested the fog net in the lab and a pilot plant, using artificial fog that had pollutants such as diesel and BPA added to it. Sure enough, the nets were able to collect about 8% of the water from the fog while removing some 94% of those pollutants. Just 30 minutes of sunlight exposure was enough to activate the titanium oxide for 24 hours, allowing it to work even in areas that receive very little sunlight.
“Our system not only harvests fog but also treats the harvested water, meaning it can be used in areas with atmospheric pollution, such as densely populated urban centers,” said Ritwick Ghosh, lead author of the study.
The team says the technology could not only be used to provide cleaner drinking water to regions that need it, but could also help recover higher quality water from steam lost to power plant cooling towers.
The research was published in the journal Nature Sustainability.
Source: ETH Zurich